Question

I’ve tried every combination to import binary data for Mongo and I CANNOT get it to work. I’ve tried using new BinData(0, <bindata>) and I’ve tried using

{
"$binary" : "<bindata>",
"$type" : "0"
}

The first one gives me a parsing error. The second gives me an error reading “Invalid use of a reserved field name.”

I can import other objects fine. For reference, I’m trying to import a BASE64-encoded image string. Here is my current version of the JSON I’m using:

{"_id" : "72984ce4-de03-407f-8911-e7b03f0fec26","OriginalWidth" : 73, "OriginalHeight" : 150, { "$binary" : "", "$type" : "0" }, "ContentType" : "image/jpeg", "Name" : "test.jpg", "Type" : "5ade8812-e64a-4c64-9e23-b3aa7722cfaa"}

Answer 1

I actually figured out this problem and thought I’d come back to SO to help anyone out who might be struggling.

Essentially, what I was doing was using C# to generate a JSON file. That file was used on an import script that ran and brought in all kinds of data. One of the fields in a collection required storing binary image data as a Base64-encoded string. The Mongo docs (Import Export Tools and Importing Interesting Types) were helpful, but only to a certain point.

To format the JSON properly for this, I had to use the following C# snippet to get an image file as a byte array and dump it into a string. There is a more efficient way of doing this for larger strings (StringBuilder for starters), but I’m simplifying for the purpose of illustrating the example:

byte[] bytes = File.ReadAllBytes(imageFile);
output = "{\"Data\" : {\"$binary\" : \"" + Convert.ToBase64String(bytes) + "\", \"$type\" : \"00\"}, \"ContentType\" : \"" + GetMimeType(fileInfo.Name) + "\", \"Name\" : \"" + fileInfo.Name + "\"}";

I kept on failing on the type part, by the way. It translates to generic binary data is specified in the BSON spec here: http://bsonspec.org/#/specification.

If you want to skip straight to the JSON, the above code output a string very similar to this:

{"Data": {"$binary": "[Byte array as Base64 string]", "$type": "00"}, "ContentType": "image/jpeg", "Name": "test.jpg"}

Then, I just used the mongoimport tool to process the resulting JSON.

Note: since I’m already in C#, I could’ve just used the Mongo DLL and done processing there, but for this particular case, I had to create the JSON files raw in the code. Fun times.